Merge pull request #1 from toolness/cukes

Fix race condition in smoke test steps, better phantom cleanup.
Add more tests, README documentation, and ability to test external URL
Removed redundant phantom subprocess tracking logic.

I realized that test/acceptance/servers.js is already ensuring
that the spawned phantom process is killed when exceptions
occur, so this basically reverts
commit f8d6fdf41f9ab00ea19548ea73a4486d5b0d239f.